The goal of this research is to increase the effectiveness of hearing aids for older adults. Despite substantial improvements in hearing aid technology, the hearing aid take-up rate and the satisfaction with fitted hearing aids has not improved in the last decade. This is partly due to a failure by the research community to produce and disseminate updated fitting methods that facilitate the ability of practitioners to exploit insights derived from basic research. The two experiments in this proposal address this issue. These experiments will produce evidence-based recommendations about amplification needs that will assist clinicians to utilize new knowledge to capitalize on the potential of existing new technologies. [unreadable] [unreadable] The first experiment explores application of laboratory research on effectiveness of high frequency gain in real-world hearing aid fittings. Recent studies have suggested that, for some individuals with high frequency hearing loss, high frequency amplification is actually detrimental for speech understanding. There is a need to verify these observations in real world settings and to devise a practical method to validly identify patients for whom high-frequency gain is contraindicated. The study assesses the prevalence of such patients, and evaluates two new procedures that have been developed to prospectively select these individuals. The two procedures are used to identify experimental and control groups comprising 20 pairs of subjects. Each subject is fitted with a hearing aid that allows comparison of two amounts of high-frequency gain. Subjects undergo laboratory testing and a field trial to determine which high-frequency gain prescription is better. Results show the extent of the problem, and whether either of the two new procedures yields accurate prediction of optimal high-frequency gain. [unreadable] [unreadable] The second experiment explores the indications for bilateral (binaural) hearing aid fittings for older adults with bilateral hearing loss. Post-fit usage patterns and self-reports indicate that about 20-30% of bilaterally fitted individuals actually benefit more from one hearing aid than two. It is not clear why some patients prefer one hearing aid over two, or which patients will fall into this category. In this study, logistic regression is used to develop a model in which binaural summation, binaural integration, binaural interference, and attitudes towards hearing aids and hearing loss are combined to predict which individuals will ultimately benefit more from one hearing aid than two. For these individuals, resources presently allocated to hearing aid purchase would be used more effectively for alternate rehabilitation methods. Outcomes of 100 bilateral hearing aid fittings will be evaluated. [unreadable] [unreadable]